One group of researchers tested a different hypothesis. They wanted to find out if aluminum, which they call “the most significant environmental contaminant of recent times,” could be another nail in the coffin for our bumblebee friends due to its status as a known neurotoxin. In humans, aluminum has been loosely linked in some studies to diseases such as Alzheimer’s. As bees rely on their cognitive function, being exposed to large doses of such a substance could be potentially catastrophic for the species.

To test their theory, researchers Christopher Exley, Ellen Rotheray and David Goulson examined 20 commercially produced colonies. After 10 weeks of monitoring the hives, the populations were frozen at minus 80 degrees Celsius. The queens, workers, males and pupae were all measured, weighed and assessed.

The frozen pupae — the bees’ inactive and immature form when transitioning from a larva to an adult — were thawed in a laboratory. After first cleaning off any surface contaminants, they were tested for aluminum content and found to contain between 13 and 200 parts per million of the toxin. The Daily Mail notes that, for humans, just 3 parts per million could be dangerous for brain tissue.

“Our data provide preliminary evidence that exposure to aluminum may be having an adverse effect on bumblebees, for colonies with high concentrations in the pupae tended to have smaller pupae,” write the authors.

“The observation here that the aluminum content of bumblebee pupae is an order of magnitude (or more) higher than levels harmful to humans gives cause for concern. Bee colonies are highly dependent on the ability of colony members to learn, navigate, and fly long distances during foraging, and so we might expect them to be particularly sensitive to neurotoxic effects.”

The researchers speculate that such a high amount of aluminum in the pupae could “interfere with the development of functioning of cognitive performance in adult bees.”

How are the bees getting dosed with the aluminum? Likely, through pollen and nectar, a bee’s bread and butter. A recent study suggested that nectar, a primary food source for bees, may be contaminated with aluminum. In experiments conducted where nectar was swapped out with a sugar solution that included aluminum, bees continued to feed, not deterred by the addition of the toxin.

Because this was a small sample, the researchers believe that further investigation should be done to find out the extent of the problem and to determine the possible consequences.

Just last month the White House announced its next steps in addressing the decline of pollinators such as honeybees, an issue that grabbed the attention of the government due to the $15 billion honeybees add in value to agricultural crops each year. The planned actions include constructing pollinator gardens at federal buildings and the restoration of millions of acres of federally managed land. The White House is also encouraging private citizens to plant pollinator-friendly plants on their own property to help provide food sources for bees, butterflies and other insects.